I couldn't find current stats, but during the 2001 NFL regular season, home teams had a record of 136-112. Home teams improved to 148-107-1 in 2002, and 157-99 in 2003. This translates into a combined win percentage of 58% for those three seasons. It seems clear that playing at home is an advantage.
This advantage ostensibly increases during the playoffs: Home playoff teams were 21-9 from 2001 through 2003 (70%), and 102-38 (73%) from 2000 through 2003. However, this apparent increase can also be attributed to the fact that in the playoffs, generally the team with the better record gets to play at home.
In any given year the chance of the home team being in the Super Bowl 6.25%; that is of course, that the Super Bowl is being played in your conferences stadium, i.e. AFC or NFC. No team has ever had home field advantage in the Super Bowl, but some teams have been close. The 1984 the 49ers played in Palo Alto, California which is 20 miles from San Fran and in Super Bowl XIV the LA Rams played in Pasedena, CA. I believe these have been the closest... but feel free to correct me if I am wrong.
Over the next 4 years, the Super Bowl is going to be held at the following team's stadiums:
2011 - Cowboys
2012 - Colts
2013 - Saints
These 5 teams are among the best in the league right now, and barring any unforeseen circumstances, they will continue to be for the next couple of year.
I want to know, how much do you think home field advantage plays into deciding the winners of games, and do you think in the next five years there will be a team that is in the super bowl in their stadium?